After an elementary video stream is decoded within a video decoder, the decoded video stream may be post-processed by a display engine and subsequently communicated to a video display, for example. As part of the post-processing functionality of a display engine, a decoded video signal may be scaled in a vertical and/or in a horizontal direction. Scaling may be utilized within the display engine to change the horizontal to vertical pixel ratio, for example, so that the decoded video signal may be conformed to the horizontal to vertical pixel ratio of the video display.
In a conventional image scaler with a scaling ratio of M:N, a polyphase filter may be utilized to generate N number of output pixels from M number of input pixels. The value N may be used to determine the number of possible phases for a given output pixel, as well as the type of filter that may be used to achieve a scaling ratio of M:N. A p-tap filter, for example, may indicate that p number of filter inputs may be utilized to generate a single filter output. During conventional scaling of a video signal, the number of possible phases for a given output pixel may be calculated on the fly. In addition, determining which input pixels may be used to generate each output pixel may also be achieved on the fly. In this way, conventional scaling may not only require significant implementation complexity, but also may lead to calculation of inaccurate phase values due to a finite arithmetic precision when calculations are made on the fly.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.